Reciprocating Internal Combustion Engines Lecture... · Day 1 (Engine fundamentals) Part 1: IC Engine Review, 0, 1 and 3-D modeling Part 2: ... Cut Plane Cummins N14 engine . . .

1 CEFRC2-4, 2014

Reciprocating Internal Combustion Engines

Prof. Rolf D. Reitz

Engine Research Center

University of Wisconsin-Madison

2014 Princeton-CEFRC

Summer School on Combustion

Course Length: 15 hrs

(Mon.- Fri., June 23 – 27, 2014)

Copyright ©2014 by Rolf D. Reitz.

This material is not to be sold, reproduced or distributed without

prior written permission of the owner, Rolf D. Reitz.

Part 4: Heat transfer, NOx and Soot Emissions

Short course outine:

Engine fundamentals and performance metrics, computer modeling supported

by in-depth understanding of fundamental engine processes and detailed

experiments in engine design optimization.

Day 1 (Engine fundamentals)

Part 1: IC Engine Review, 0, 1 and 3-D modeling

Part 2: Turbochargers, Engine Performance Metrics

Day 2 (Combustion Modeling)

Part 3: Chemical Kinetics, HCCI & SI Combustion


Day 3 (Spray Modeling)

Part 5: Atomization, Drop Breakup/Coalescence

Part 6: Drop Drag/Wall Impinge/Vaporization/Sprays

Day 4 (Engine Optimization)

Part 7: Diesel combustion and SI knock modeling

Part 8: Optimization and Low Temperature Combustion

Day 5 (Applications and the Future)

Part 9: Fuels, After-treatment and Controls

Part 10: Vehicle Applications, Future of IC Engines


2 CEFRC2-4, 2014

Scorching Detonation Cracking

Engine heat transfer

Up to 30% of the fuel energy is lost to wall heat transfer

Can influence engine ignition/knock

Engine durability – catastrophic engine failure

Challen, 1998

3 CEFRC2-4, 2014


Heat transfer

c s r

II p Q Q Q

t

u u J

Gas phase energy equation

Radiation source term

4

, 4r

bQ I d I

Ω

r r Ω Ω r

* *ln 2.1 33.34

2.1ln 2.5

g p g g w

w

C u T T T y G uq

y

* ln

2.1ln 2.5

p g g w

w

C u T T Tq

y

2.12.1w

g p

qdTG

dy C y

2.1 * ln

2.1ln 2.5

gg

w

Tu T

TdT

dy y y

Wall heat flux (account for compressibility)

With radiation Without radiation

G radiative heat flux = qwr

Han, 1995

Wang, 2012

4 CEFRC2-4, 2014

wall

Dy

qw

* /y yu D u*


Radiation modeling

Radiation Transfer Equation:

Scattering terms, , S ~ usually neglected compared to absorption

Radiation intensity at wall

surface emissivity

, , ,4

snet s bI a I I S

Ω r Ω r Ω r r Ω

net absorption coefficient, scattering coefficient netas

net sa extinction coefficient

4

wb

TI

r

4

0

,r

w wG q I d T

n Ω

n Ω r Ω Ω

Back body radiative flux (independent of angle)

Discrete ordinates model

1

4nDir

r m m

b

m

Q I I

r r r

s

Wiedenhoefer, 2003

5 CEFRC2-4, 2014


Soot and gas absorption

Total absorption coefficient

Soot absorption

Wide band model for CO2 and H2O

2 2net soot CO H Oa a a

-11260 msoot soota C T CO2 absorption bands

2

3

1

2,

1b band center C T

band center

CT

e

1

, , ln 1 , ,g e g e

e

a T P L T P LL

2 2

1 1 1 1 1fuel CO CO H O

Importance of soot:

1gasa

T soota T

4

4

, 4r

b gas sootQ a I d I a a T

Ω

r r Ω Ω r 3 5

gas sootT T

6 CEFRC2-4, 2014

Part 4: Heat transfer, NOx and Soot Emissions Wiedenhoefer, 2003a

Wall heat transfer

Conjugate heat transfer modeling

ERC - Heat Conduction in Components code (HCC)

Iterative coupling

between HCC

and CFD code

Unstructured

HCC Mesh

Wiedenhoefer, 2000

7 CEFRC2-4, 2014


8 CEFRC2-4, 2014

Wall heat transfer

Cut Plane

Cummins N14 engine

. . . . . . . . .

Caterpillar SCOTE engine

Wiedenhoefer, 2000 Part 4: Heat transfer, NOx and Soot Emissions

-20 -15 -10 -5 0

560

580

600

620

640

660

680

700

720

740

No Radiation

Run 1

Run 2

Run 3

With Radiation

Run 1

Run 2

Run 3

Pe

ak P

isto

n T

em

pe

ratu

re [

K]

Start of Injection, ATDC

F = 0.7

Predicted piston temperature - CDC

Effect of radiation on wall heat loss

Total heat loss increased by 30% due to

radiation.

34% - head, 19% - liner, 47% - piston.

Lowers bulk gas temperatures

Results in lower NOx and higher soot

NOx reduced by as much as 30% (ave)

-20 -15 -10 -5 0

2

4

6

8

10

12

14

16

NO

x [

g/k

Wh

]

Start-of-injection, ATDC

F = 0.5

Uniform Temp / No rad

Non-uniform Temp / With Rad

F = 0.7

Uniform Temp / No rad

Non-uniform Temp / With Rad

Wiedenhoefer, 2003

9 CEFRC2-4, 2014


Exhaust Surge Tank

#4

#3

#2

#1

4-cylinder engine head cylinder #1,3,4 deactivated

Horiba Hydrocarbon

Analyzer

Horiba Analyzers NOx CO O2

Exhaust CO2 Intake CO2

AVL 415S Smoke Meter

DC Dyno

Port Fuel

Injectors

Barrel Heater

Air Heater

Intake Surge Tank

Dry Compressed Air

Chilled Water

Water Heater

EGR Heat Exchanger

Direct Injector

Swirl Control Valves

Choked Flow Orifices

Engine Geometry

Base Engine GM 1.9L Diesel

Compression Ratio 16.3

Displacement (Liters) 0.477

Stroke (mm) 90.4

Bore (mm) 82

Intake Valve Closing -132° aTDC

Exhaust Valve Opening 112° aTDC

Swirl Ratio 1.5 -4.8

Piston Bowl Type

Stock (Re-

entrant)

Port Fuel Injectors

Included Spray Angle 20°

Injection Pressure (bar) 2 to 10

Rated Flow (cc/sec) < 10

Bosch Common Rail Injector

Number of Holes 7

Hole Diameter (mm) 0.14

Included Spray Angle 155°

Injection Pressure (bar) 250 to 1000 bar

10 CEFRC2-4, 2014

Wall heat flux measurements

Gingrich, 2014 Part 4: Heat transfer, NOx and Soot Emissions

1

2 3

4

5 6

7

Receiver

Data Acqusition

Power Converter

Primary Coil (Engine

Mounted)

Secondary Coil

(Piston Mounted)

Transmitter

Thermocouples

Inductive PowerSupply

Piston

11 CEFRC2-4, 2014

( ) [ cos( ) sin( )]m n nT t T A n t B n t

1

( ) [( )cos( ) ( )sin( )]2

N

m l n n n n

n

k nq T T k A B n t A B n t

l

Dynamic Steady

• Fourier analysis is applied to find dynamic heat flux

• Integral of the dynamic heat flux over the full cycle is zero

Part 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014

Mode 1 Mode 2 Mode 3 Mode 4

Speed (RPM) 1490 1900 2300 2300

IMEPg (bar) 4.2 5.7 5.7 8

CA50 (degATDC) 4 5 4.5 8

Swirl 1.5 1.5 1.5 1.5

Intake Temperature (C) 75 50 50 35

Intake Pressure (kPa) 115 130 130 188

ERG (%) 0 0 0 55

Regime Fuel

HCCI 91PON Gasoline / n-heptane

RCCI F76 / 91PON Gasoline

CDC F76

Combustion strategy effects - CDC / HCCI / RCCI

Fuels:

12 CEFRC2-4, 2014

Part 4: Heat transfer, NOx and Soot Emissions Gingrich, 2014

Mode 3

-20 -10 0 10 20 30 40

0

50

100

150

Crank Angle [deg]

AH

RR

[J/d

eg

]

Heat Release Rate

-20 -10 0 10 20 30 40

0

1

2

3

4

5x 10

6

Crank Angle [deg]

Heat F

lux [W

/m2]

Location 7

Tm

=191.8C

Tm

=182.1C

Tm

=158.5C

-20 -10 0 10 20 30 40

0

1

2

3

4

5x 10

6

Crank Angle [deg]

Heat F

lux [W

/m2]

Location 3

Tm

=169.1C

Tm

=155.4C

Tm

=140.6C

-400 -200 0 200 400120

125

130

135

140

145

150

Crank Angle [deg]

Tem

pera

ture

[C

]

Location 3 Temperature

CDC

HCCI

RCCI

5.7 bar IMEPg

5 deg ATDC CA50

2300 rev/min

13 CEFRC2-4, 2014


Combustion strategy effects Heat release rate

Gingrich, 2014

1 2 3 40

1000

2000

3000

4000

5000

6000

Mode

Inte

gra

ted

He

at F

lux [J/m

2]

Location 3

CDC

HCCI

RCCI

1 2 3 40

1000

2000

3000

4000

5000

6000

Mode

Inte

gra

ted

He

at F

lux [J/m

2]

Location 7

CDC

HCCI

RCCI

1 2 3 40

1000

2000

3000

4000

5000

6000

Mode

Inte

gra

ted

He

at F

lux [J/m

2]

Location 7

CDC

HCCI

RCCI

1 2 3 40

1000

2000

3000

4000

5000

6000

Mode

Inte

gra

ted

He

at F

lux [J/m

2]

Location 7

CDC

HCCI

RCCI

14 CEFRC2-4, 2014


Combustion strategy effects - CDC / HCCI / RCCI

Heat losses significantly less with low temperature combustion strategies

Gingrich, 2014

Compare CDC and RCCI

combustion at matched

CA50, load, Φg

(4.6°CA ATDC, 0.35)

RCCI piston heat flux

measured to be lower

than CDC

Area integrated HX and

temp. determined RCCI

CDC

Hendricks, 2014

CDC RCCI

∫Piston HX fuel

energy (%)

7.7 5.9

GTE (%) 51.2

52.7

Heavy-duty diesel heat flux data

15 CEFRC2-4, 2014


Engine emissions - transportation & toxic air pollutants

Toxic air pollutants - Hazardous Air Pollutants or HAPs known to cause or

suspected of causing cancer or other serious health ailments. - Clean Air Act Amendments of 1990 lists 188 HAPs from transportation.

In 2001, EPA issued Mobile Source Air Toxics Rule:

- identified 21 MSAT compounds.

- a subset of six identified having the greatest influence on health: benzene, 1,3-butadiene, formaldehyde, acrolein, acetaldehyde,

and diesel particulate matter (DPM).

Harmful effects on the central nervous system:

BTEX/N/S - benzene, toluene, ethylbenzene, xylenes, Naphthalene, Styrene

Criteria air contaminants (CAC), or criteria pollutants - air pollutants that cause smog, acid rain and other health hazards.

EPA sets standards on:

1.) Ozone (O3),

2.) Particulate Matter (soot): PM10, coarse particles: 2.5 micrometers (μm) to 10 μm in size

PM2.5, fine particles: 2.5 μm in size or less

3.) Carbon monoxide (CO), 4.) Sulfur dioxide (SO2),

5.) Nitrogen oxides (NOx), 6.) Lead (Pb)

16 CEFRC2-4, 2014


Engine emissions - transportation & toxic air pollutants

17 CEFRC2-4, 2014

Part 4: Heat transfer, NOx and Soot Emissions Curtis, 2014

Diesel emission solutions – Selective Catalytic Reduction (SCR) and Diesel Particulate Filter (DPF)

EGR?

SCR? Cummins Cu-Zeolite with DEF for 2010

Claim 3-5% fuel economy gain (Class 8 truck 1% ≈$1,000 per year)

“StableGuard Premix” dose rate ~2% of fuel consumption rate

Cost? $3/gal? AdBlue at pump in Germany $12/gal

Volvo announced surcharge of $9,600 for 2010 compliance

(complex – dosing rate, DEF freezes at 12F, gasifies at 130F)

Plus $7,500 for 2007 compliance AT system cost equals cost of engine!

Navistar – no SCR

Enabling technologies (Cost?):

Improved combustion bowl design - PCCI

Improved EGR valves, air-handling, VVA

Twin-series turbochargers, inter-stage cooling

High-pressure CR fuel injection (31,800 psi)

US EPA 2010 HD soot: 0.0134 g/kW-hr

NOx: 0.2682 g/kW-hr.

1.)

2.)

18 CEFRC2-4, 2014


Zeldo’vich thermal NOx mechanism

ERC 12-step NOx model is based on GRI-Mech v3.11 and includes:

Thermal NOx

Prompt NOx around 1000 K.

Extensions

NO can convert HCN and NH3

Interaction between NO and Soot

NOx modeling

Rate controlling step due to high N2 bond strength

Yoshikawa, 2008

Zeldovich, 1946

Fenimore, 1979

Eberius, 1987

Guo, 2007

19 CEFRC2-4, 2014


ERC 12 step NOx Mechanism

SENKIN2 used to predict species histories.

XSENKPLOT used to visualize reaction pathways and identify important reactions and species.

Reduced mechanism validated for test temperatures from 700K to 1100 K and equivalence ratios from 0.3 to 3.0.

Four additional species (N, NO, N2O, NO2) and 12 reactions added to ERC PRF mechanism

Kong, 2007

Detailed mechanism: Smith, GRI-mech, 2005

20 CEFRC2-4, 2014


ERC 12 step NOx mechanism

2

2

2 2 2

2

2 2

2 2 2

2 2

2 2

2

2 2

2

N NO N O

N O NO O

N + OH NO H

N O O N O

N O O 2NO

N O H N OH

N O OH N HO

N O M N O M

HO NO NO OH

NO O M NO M

NO O NO O

NO H NO OH

GRI mechanism results Reduced mechanism results

Comparison of NOx predictions (T=900K, P=3.7MPa)

Diesel spray computations

Detailed mechanism: Smith, GRI-mech, 2005

21 CEFRC2-4, 2014

Part 4: Heat transfer, NOx and Soot Emissions Kong, 2007

CH radical and HCN bridge in fuel-rich regions

Tini=769K

Pini=40bar

Time=100ms

φ=1.0 φ=3.0 N group

CxHy group

Constant

volume

SENKIN

analysis with

ERC n-heptane

mechanism &

GRI ver.3 NOx

mechanism

Absolute Flux

normalized to

NO by

XSENKPLOT

Competing?

Yoshikawa, 2008

22 CEFRC2-4, 2014


23

Influence of soot radiation on combustion and NOx

BW: measured

Colored: prediction

Yoshikawa, 2009

Musculus, 2005

23 CEFRC2-4, 2014


0

2

4

6

8

-15 -10 -5 0 5 10 15 20SOI [CAD]

Max S

INL [a.u

.]

Model w/ radiation

Musculus (2005)

0

20

40

60

80

100

120

140

-15 -10 -5 0 5 10 15 20

SOI [CAD]

NO

x [g/k

gfu

el]

Musculus (2005)

0

10

20

30

40

50

60

70

80

-15 -10 -5 0 5 10 15 20

SOI [CAD]

NO

x [g/k

gfu

el]

Model w/o radiation

Model w/ radiation

Model w/o soot and radiation

Measured

soot

Predicted

“NOx bump”

“NOx bump” not observed in prediction, but

reduction in predicted NOx seen with retard of

SOI (~ SOI=8 CAD ATDC)

Radiation lowers predicted NOx ~ 7.5 %

Absence of soot lowered predicted NOx ~ 2.5 %

NOx model underpredicts measured NOx

Magnitude sensitive to turbulent Schmidt #

Influence of soot radiation on combustion and NOx

Yoshikawa, 2009

24 CEFRC2-4, 2014


Particulate emissions

25 CEFRC2-4, 2014

Regulated emissions PM2.5

Greatest health risk - fine particles

can lodge deeply into the lungs

New challenge - engines must meet

particulate number-based regulations (PN).

Euro 6:

PN limit 6.0e11 particles/km for vehicles

produced after 2017.

California Air Resources Board (CARB)

LEV III:

Total PM mass: 3.8 mg/km for 2014

and 1.9mg/km for 2017

PN: 3.8e12 and 1.9e12 particle/km.

Part 4: Heat transfer, NOx and Soot Emissions Kittelson, 1998

Soot modeling at the ERC

Soot models

Two-step model Multi-step

Phenomenological

(MSP) model

PAH chemistry

Patterson, SAE 940523

Kong, ASME 2007

Vishwanathan & Reitz, SAE

2008-01-1331

Vishwanathan & Reitz, 2009

Kazakov & Foster, SAE 982463

Tao, 2009

Tao, SAE 2006-01-0196

Tao, 2006

Vishwanathan & Reitz, SAE 2008-

01-1331

Vishwanathan &

Reitz, CST 2010

Models of soot formation/oxidation – Kennedy, Prog. Energy Comb. Sc., 1997

Soot processes in engines - Tree and Svenson, Prog. Energy Comb. Sc., V2007

26 CEFRC2-4, 2014


ssf so

d(M )=M -M

dt

0.5

sf sf sf C2H2M =A P exp(-E /RT) M

so nsc s

s nom

6M = W M

ρ D

Two-step model

Hiroyasu soot formation

Nagle and Strickland-Constable (NSC)

oxidation

Net soot mass

C2H2 soot precursor

ρs = Soot density = 2 g/cm3

Dnom = assumed nominal soot diameter

= 25 nm

Wnsc = NSC oxidation rate/area

Mc2h2 = C2H2 Mass, Ms = Mass of soot

“tuning” constant

Hiroyasu & Kadota, SAE 760129

Nagle & Strickland-Constable, 1962

27 CEFRC2-4, 2014


SANDIA spray chamber:

Vishwanathan, 2008

C2H2 inception occurs at lift-off location

Inclusion of PAH chemistry needed for accurate prediction of soot form/oxid.

Soot mass comparison

0

0.5

1

1.5

2

0 20 40 60 80 100 120

Distance from Injector (mm)

So

ot

Ma

ss (

mic

ro g

ms)

Expt.

Model

Model predicted soot inception location

→ Lift-off length position

Performance of two-step soot model

Pickett, 2004

28 CEFRC2-4, 2014


HCHO flame soot

10 mm 90 mm

100 mm 0 mm

Heptane

injection

C2H2 inception occurs at lift-off location

Inclusion of PAH chemistry needed for accurate prediction of soot form/oxid.

Performance of two-step soot model

Sandia experiment

Model

Pickett, 2004

29 CEFRC2-4, 2014

Part 4: Heat transfer, NOx and Soot Emissions Vishwanathan, 2008

Vishwanathan, 2008

30 CEFRC2-4, 2014

Phenomenological

soot models


Reduced PAH mechanism

Reduced PAH mechanism of Xi & Zhong, 2006 based

on detailed mechanism of Wang &Frenklach, 1997 was

integrated (20 species and 52 reactions)

A1 formation through propargyl radical (C3H3)

Higher aromatics formed through HACA scheme

(hydrogen abstraction, carbon addition)

Reaction Arrhenius parameters-A, n, E. (Units of A in mole-

cm-sec-K and units of E in cal/mole)

C3H3 + C3H3 → A1 2.0E+12, 0.0, 0.0

A1- + C4H4 ↔ A2 + H 2.50E+29, -4.4, 26400.0

A1+ A1-↔ P2 + H 1.10E+23, -2.9, 15890.0

A2-1 + C4H4 ↔ A3 + H 2.50E+29, -4.4, 26400.0

A1C2H* + A1 ↔ A3 + H 1.10E+23, -2.9, 15890.0

A3-4 + C2H2↔ A4 + H 3.00E+26, -3.6, 22700.0

A1 = benzene, A2 = naphthalene, P2 = biphenyl, A3 = phenanthrene, A4= pyrene, A1- = phenyl,

A2-1 = 1-naphthyl, A3-4 = 4-phenanthryl, A1C2H* = phenylacetylene radical

Vishwanathan, 2009

31 CEFRC2-4, 2014


Amount of dry-carbon mass locked-up in aromatic precursors small compared to

measured soot

PAH species

0 20 40 60 80 100

1E-5

1E-4

1E-3

0.01

0.1

1

Expt. soot mass

A4

A3

A2

A1

C2H

2

Soo

t/C

arbo

n m

ass

in p

recu

rsor

s (

g)

Distance from Injector (mm.)

15% O2

X=0 mm X=85 mm

Soot mass fraction

15% O2, A3 is precursor

Expt.

CFD

Improvement in soot location

Reduced PAH mechanism implemented considering up to 4 aromatic rings (pyrene)

- A3 (Phenanthrene) used as precursor for soot formation model

~ peak of 0.016 ppm

Sandia expts: Pickett & Idicheria, 2006

32 CEFRC2-4, 2014


Soot model implementation

1. Soot inception through A4:

2. C2H2 assisted surface growth:

3. Soot coagulation:

1 1 1ω -1= k [A ], k = 2000 {s }4

2 2 2 2 2

p

ω { }

N { }p

{

4 -1= k [C H ], k = 9.0 10 exp(-12100/T) S s

2 -1S = πd cm

1/36Y ρ

c(s)d = cm}

πρ Nc(s)

Surface area per

unit volume

Particle size

Graphitization

YC(S) = soot mass fraction

N = soot number density (per cc)

ρC(S) = 2.0 gm/cm3

MC(S) = MW of carbon

Kbc = Boltzmann’s constant

Ca = agglomeration constant = 9

1ωC H (A ) 16C(s) + 5H 16 10 4 2

2ωC(s) +C H 3C(s) + H2 2 2

3ωnC(s) C(s)n

3

1/6 1/26M ρY6K Tc(s) c(s) 1/6 11/6 -3 -1bcω = 2C [ ] [N] {particles cm s }aπρ ρ Mc(s) c(s) c(s)

Mono –disperse locally: All soot in a comp. cell have same diameter

Vishwanathan, 2010

Leung, 1991

Leung, 1991

33 CEFRC2-4, 2014


4. O2 assisted soot oxidation (NSC model):

5. OH assisted oxidation (Modified Fenimore and Jones model):

4c(s)

K PA O12 -3 -12ω = x+K P (1-x) S {mol cm s }B OM 1+K P 2Z O2

x = P (P + (K /K ))T BO O2 2

-2 -1 -1K = 30.0 exp (-15800/T) {g cm s atm }A

-3 -2 -1 -1K = 8.0 10 exp (-7640/T) {g cm s atm }B

5 -2 -1K = 1.51 10 exp (-49800/T) {g cm s }T

-1K = 27.0 exp (3000/T) {atm }Z

-1/25 OH OH

-3 -1 ω = (12) 10.58 γ X T S {mol cm s }

x = fraction of A sites

(1-x) = fraction of B sites

PO2 = partial pressure of O2

KA,B,T,Z = rate constants

XOH = mole fraction of OH

γOH = OH collision efficiency = 0.13

41 ωC(s) + O CO22

52

1ωC(s) + OH CO + H

2


Fenimore, 1967

34 CEFRC2-4, 2014


6. PAH-assisted surface-growth

k = number of carbon atoms and j = number of hydrogen atoms,

γks = 0.3 is the collision efficiency between soot and PAH, βks = collision frequency,

di = collisional diameter of PAH, dA = size of single aromatic ring = 1.393√3 Ǻ,

μi,j = Reduced mass of colliding species = Mass of PAH,

mi = mass of PAH expressed in terms of number of carbon atoms - k

Most models consider only mono-aromatic benzene as growth species.

6ω

k,j 2 6 ks ks k,j

jC(s) + PAH C(s+k) + H , ω = γ β PAH N

2

2 3 -1bcks p PAH

i,j

π K Tβ = 2.2 (d + d ) cm s

2 μ

iPAH A

2md = d

3


35 CEFRC2-4, 2014


7. Transport equations:

M = ρYc(s) (soot species density) and N (number density) with N being treated

as passive species

Thermophoresis term implemented as a source term

dnuci = 1.25 nm (~100 carbon atoms)

M

M μ M μ TM ξ M S

SC ρ ρ Tv

t

πηξ=0.75 (1+ ) , η = 0.9

8

M 1 2 6 4 5 c(s)-3 -1S = 16ω + 2ω +6ω - ω - ω M {g cm s } for ρYc(s)

M 1 3

Mc(s) -3 -1S = 16ω - ω {particles cm s } for NMnuci

π 3 M = d ρ nuci nuci c(s)6

Thermophoresis Source terms diffusion convection


36 CEFRC2-4, 2014


37 CEFRC2-4, 2014

Jiao, 2014

70,000 cells at BDC,

including the intake

and exhaust manifolds

and cylinders.

Spark plug: at center of cylinder head.

Completely homogeneous fuel/air mixture at IVC

Experiment: EPA Tier II EEE certification fuel, 28% aromatics.

ERC KIVA code simulations:

DPIK ignition model, G-Equation combustion model.

Fuel: iso-octane/28% toluene by volume.

MultiChem mechanism:

ic8h18/nc7h16/c7h8/PAH (79 species & 379 reactions)

Soot mass and particle diameter prediction

Premixed charge SI engine particulate modeling


•38

Soot formation prediction

-40 -20 0 20 40 60 80

0.00

0.01

0.02

0.03

0.78; 0.26

0.98; 0.33

1.2 ; 0.41

1.3 ; 0.44

1.4 ; 0.48

1.5 ; 0.51

Incylin

de

r soo

t (g

/kg-f

)

Crank Angle (deg)

F; C/O

680 700 720 740 760 780 800 CAD

Predicted soot mass no longer reduces significantly after 80 ATDC.

Soot produced at 80 ATDC increases with increase of φ.

Soot formation dominates first and then soot oxidation begins to

play a key role. Peak in-cylinder soot mass increases w/ an

increase of φ.

38 CEFRC2-4, 2014

Part 4: Heat transfer, NOx and Soot Emissions Jiao, 2014

-4 -3 -2 -1 0 1 2 3 4500

1000

1500

2000

2500

3000

3500 Incylinder temperature

G (-)

T

em

pe

ratu

re (

K)

Radial position (cm)

TDC

-2

-1

0

1

2

3

4

G (-)

-4 -3 -2 -1 0 1 2 3 40

5x10-10

1x10-9

2x10-9

2x10-9

C2 H

2 mass fra

ctio

n (-)

A4 m

ass fra

ction

(-)


A4 mass fractionTDC

0

1x10-4

2x10-4

3x10-4

4x10-4

5x10-4

6x10-4

C2H

2 mass fraction

TDC φ =1.5

C2H2

A4

----------------burnt-----------------

----------------burnt-----------------

39 CEFRC2-4, 2014


-4 -3 -2 -1 0 1 2 3 40

1x10-6

2x10-6

3x10-6

4x10-6

Soot mass fraction


TDC

10-6

10-5

10-4

10-3

10-2

10-1

100

101

O2 mass fraction

OH mass fraction

O2 , O

H m

ass fra

ctio

n (-)

Soo

t m

ass fra

ction

(-)

-4 -3 -2 -1 0 1 2 3 41x10

-21x10

01x10

21x10

41x10

61x10

81x10

101x10

12

TDC Number density

Nu

mbe

r density (

#/c

m3)

Partic

le s

ize

(nm

)


0

100

200

300

400

Particle size

TDC φ =1.5

nd

dp

O2

OH soot

---------------burnt-------------

---------------burnt-------------

40 CEFRC2-4, 2014


-4 -3 -2 -1 0 1 2 3 40

2x10-7

4x10-7

6x10-7

8x10-7

1x10-6

Soot mass fraction


800 aTDC

0

2x10-5

4x10-5

6x10-5

8x10-5

1x10-4

O2 mass fraction

OH mass fraction

O2 , O

H m

ass fra

ctio

n (-)

Soo

t m

ass fra

ction

(-)

-4 -3 -2 -1 0 1 2 3 41x10

-2

1x100

1x102

1x104

1x106

1x108

800 aTDC

Number density

Nu

mbe

r density (

#/c

m3)

Partic

le s

ize

(nm

)


0

100

200

300

400

500

Particle size

800 ATDC φ =1.5

soot

O2

OH

dp

nd

41 CEFRC2-4, 2014


10 1001x10

2

1x103

1x104

1x105

1x106

1x107

1x108

1x109

1x1010

dN

/dlo

g(d

p)

(#/c

m3)

dp (nm)

FC/O

reference

expt

Experiment [1] Simulation

Nearly identical PSDs until about φ =1.3,

nd sharply declines with increase of dp.

When φ >1.3, nd consistently increases

with increasing φ , and decreases gradually

with increasing dp.

For φ <1.4, shape of PSDs is very flat and broad,

which is different from experiment, but looks

like PSDs for A/F of 14.6 for engine loads

lower than 4 bar in Ref. [2].

For φ =1.4 and 1.5 , magnitude of nd of small

particles are well represented, nd decreases

with increasing dp.

[1] Hageman, 2013. [2] Maricq, 1999

10 1001x10

2

1x103

1x104

1x105

1x106

1x107

1x108

1x109

1x1010

Avera

ged p

art

icle

num

ber

density (

#/c

m3)

dp (nm)

FC/O

42 CEFRC2-4, 2014


Particulate size distributions

SANDIA optical engine – HTC/LTC

Engine Parameter

Bore x stroke (cm) 13.97 x 15.24

Speed (rpm) 1200

Compression ratio (CR) 11.2:1

Swirl ratio 0.5

Number of nozzle holes 8

Orifice diameter (mm) 0.196

Included angle 152°

Fuel Diesel #2

Sector angle 45

HTC-diff./

premixed

LTC

Early/late

Amb. O2 % 21 12.7

SOI -7/-5 -22/0

Pin (bar) 2.33/1.92 2.14/2.02

Tin (C) 111/47 90/70

Fuel (mg) 61 56

Pinj (bar) 1200 1600

Expt. Data: Singh, 2007

Vishwanathan, 2010

43 CEFRC2-4, 2014

Soot in stratified charge engines


SNL optical engine – HTC/LTC

HTC-Diffusion

LTC-Early inj.

Diffusion to premixed combustion, soot ↓

HTC to LTC, soot ↓

In-cylinder soot formation/oxidation

Difference in HTC and LTC soot amounts well

captured

-10 -5 0 5 10 15 20 25 30 35 40 45 500

2

4

6

8

10

12

14

16

18

20 HTC-Diffusion

HTC-Long ignition delay

LTC-Early injection

LTC-Late injection

Solid - Expt. (Singh et al. 2007)

Dashed - Model Predicted

In-c

ylin

der

soot

(g/k

g-f

)

CAD ATDC

-50 -40 -30 -20 -10 0 10 20 30 40 500

2

4

6

8

10 Expt. (Singh et al. 2007)

Model Predicted

CAD ATDC

Pre

ssure

(M

Pa)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400H

RR

(J/D

eg)

-50 -40 -30 -20 -10 0 10 20 30 40 500

2

4

6

8

10

HR

R (

J/D

eg)

Expt. (Singh et al. 2007)

Model Predicted

Pre

ssure

(M

Pa)

CAD ATDC

0

100

200

300

400

500

600

700

800

900

1000

44 CEFRC2-4, 2014


Expt. Data: Singh, 2007

Summary and current directions

Integration of soot model with multi-component vaporization and chemistry models

Extension to GDI and H/P/RCCI

Organic fraction modeling:

OF correlates with premixedness

Soot diameter comparisons with TEM

measurements obtained from various

combustion modes

Inception

H2 +

C2H2 assisted surface

growth

Coagulation

Coa

gula

tion

Oxidation by OH

Oxidation by O2

+ CO

+ H2

Gasoline/Diesel

Fuel-aromatic assisted

surface growth

H2 +

Need development/improvement

Fuel breakdown + fuel

aromatic led PAH growth

45 CEFRC2-4, 2014


Reciprocating Internal Combustion Engines Lecture... · Day 1 (Engine fundamentals) Part 1: IC Engine Review, 0, 1 and 3-D modeling Part 2: ... Cut Plane Cummins N14 engine . . .

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